1. Field of the Invention
The present invention relates to a transmissive screen for a rear projection display apparatus and the rear projection display apparatus.
2. Description of the Related Art
A rear projection display apparatus has been widely used as a kind of image display apparatus with a large screen. As is known, using a rear projection display apparatus, image light emitted from an image light source such as a CRT, LCD device, DLP (Digital Light Processing) device or the like is magnified and projected from the rear side to be viewed from the front side of a transmissive screen.
Lately, there has been a great demand for a thin rear projection display apparatus. Accordingly, there is considered a rear projection display apparatus in which an eccentric optical system is used where the center of screen (the center of a transmissive screen) may not correspond with a light axis.
A transmissive screen typically includes a Fresnel lens and a lenticular lens. A Fresnel lens includes minute prisms arranged in a concentric pattern, having the function of parallelizing image light radially incident from a mirror. There are two kinds of Fresnel lens, one of which uses refraction and the other of which uses partial reflection. In general, a Fresnel lens of partial reflection is used for a rear projection display apparatus including an eccentric optical system.
A lenticular lens has the function of expanding a viewing angle by deflecting incident light. Typically, there is used a horizontal lenticular lens with which the viewing angle in the horizontal direction is expanded (in which a plurality of cylindrical lenses are arrayed with the lengthwise direction thereof being directed in the vertical direction of a screen). However, in order to expand the viewing angle in the vertical direction as well, a vertical lenticular lens (in which a plurality of cylindrical lenses are arrayed with the lengthwise direction thereof being directed in the horizontal direction of a screen) may be used in addition to the horizontal lenticular lens.
Hereupon, with a transmissive screen being configured to have horizontal and vertical lenticular lenses as well as a Fresnel lens, a concentric pattern of the Fresnel lens and a lattice pattern formed by the horizontal and vertical lenticular lenses interfere with each other, which may cause moiré.
In the past, Japanese Published Patent Application No. 10-48404 (paragraphs 0021, 0147, 0160 and FIG. 1) discloses, for example, technology for reducing generation of moiré in a transmissive screen for a rear projection display apparatus, in which the transmissive screen includes a planar lens having a transparent micro-sphere arranged layer on a transparent substrate. However, replacing a lenticular lens with such planar lens is different from reducing generation of moiré in a transmissive screen provided with a Fresnel lens and a lenticular lens.
Further, a transmissive screen including horizontal and vertical lenticular lenses as well as a Fresnel lens typically has a structure in which the following three board members are superimposed:
(i) a board member including a substrate and a Fresnel lens;
(ii) a board member including a substrate and a horizontal lenticular lens; and
(iii) a board member including a substrate and a vertical lenticular lens.
However, preparing a transmissive screen with three board members may increase production costs due to an increase in the number of components used and an increase in takt time. Further, with three board members being superimposed, the number of interfaces between those members may increase and cause light to be reflected thereon. Therefore, luminance may be lowered and stray light may increase, causing ghost which reduces the picture quality.